Known processes for the production of lithium carbonate from lithium containing ores or concentrates typically utilise the thermal treatment of an alpha-spodumene ore or concentrate. This thermal treatment can be referred as decrepitation and transforms the alpha-spodumene to beta-spodumene which is in turn able to be solubilised by acid. The step in which the beta-spodumene is solubilised in acid takes place in a kiln and produces soluble lithium salt. The lithium salt is passed to one or more tanks in which the lithium salt is purified. Leached crude lithium salt is subsequently passed to a step in which the pH of the slurry is adjusted, whereby certain impurities, including iron and magnesium are intended to be precipitated. Thus purified lithium salt is treated with soda ash to produce lithium carbonate. This lithium carbonate can be further treated with hydrated lime to produce lithium hydroxide.
Processes for the production of lithium carbonate and lithium hydroxide from brines typically involves the use of evaporation ponds to increase the concentration of the salts contained therein before being passed to a series of steps aimed to reduce the impurities present.
The above described processes of the prior art are relatively inefficient in the removal of impurities remaining in the pregnant leach solution, which results in a relatively impure lithium hydroxide and lithium carbonate product. This is particularly problematic when attempting to produce high quality or battery grade lithium hydroxide and lithium carbonate products.
The process of the present invention has as one object thereof to overcome substantially one or more of the above mentioned problems associated with prior art processes, or to at least provide a useful alternative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. This discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
The term “battery grade lithium carbonate” refers to a product having a purity of about 99.5% or higher. Similarly, the term “battery grade lithium hydroxide” refers to a product having a purity of about 99% or higher.